a modified route discovery approach for dynamic source routing (dsr) protocol in mobile ad-hoc...
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International Journal of Software Engineering and Computer Systems (IJSECS)
ISSN: 2289-8522, Volume 3, pp. 17-30, February 2017
©Universiti Malaysia Pahang
DOI: http://dx.doi.org/10.15282/ijsecs.3.2017.2.0024
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A MODIFIED ROUTE DISCOVERY APPROACH FOR DYNAMIC SOURCE
ROUTING (DSR) PROTOCOL IN MOBILE AD-HOC NETWORKS
Alaa Azmi Allahham1 and Muamer N. Mohammed1,2
1Faculty of Computer Systems and Software Engineering University Malaysia Pahang,
26300 Kuantan, Pahang, Malaysia 2IBM Center of Excellence, University Malaysia Pahang, 26300 Kuantan, Pahang,
Malaysia
e-mail: [email protected], [email protected]
ABSTRACT
Mobile Ad-hoc networks (MANETs) involved in many applications, whether
commercial or military because of their characteristics that do not depend on the
infrastructure as well as the freedom movement of their elements, but in return has
caused this random mobility of the nodes many of the challenges, where the routing is
considered one of these challenges. There are many types of routing protocols that
operate within MANET networks, which responsible for finding paths between the
source and destination nodes with the modernization of these paths which are constantly
changing due to the dynamic topology of the network stemming from the constant
random movement of the nodes. The DSR (Dynamic Source Routing) routing protocol
algorithm is one of these routing protocols which consist of two main stages; route
discovery and maintenance, where the route discovery algorithm operates based on
blind flooding of request messages. blind flooding is considered as the most well
known broadcasting mechanism, it is inefficient in terms of communication and
resource utilization, which causing increasing the probability of collisions, repeating
send several copies of the same message, as well as increasing the delay. Hence, a new
mechanism in route discovery stage and in caching the routes in DSR algorithm
according to the node's location in the network and the direction of the broadcast is
proposed for better performance especially in terms of delay as well as redundant
packets rate. The implementation of proposed algorithms showed positive results in
terms of delay, overhead, and improve the performance of MANETs in general.
Keywords: MANET; DSR Protocol; Threshold, Broadcasting
INTRODUCTION
A wireless Ad-hoc network (WANET) is a decentralized type of wireless network (Lin,
1999), where WANET networks such as home and sensor networks have become an
important part of our daily life and are expected to provide multimedia services, which
increases the demand for higher data rates, higher link reliability, and longer battery life.
The main feature of these types of networks is self-organization (distributed), and these
features reduce the cost and effort of their configuration and maintenance.
Ad hoc networks have a wide range of applications for both the military and the civilian
world. It is used for enhancing military communication in the battlefield or in areas hit
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by natural catastrophes. Furthermore, are used to provide wireless communications
infrastructure in different areas as a fast, deployable, temporary replacement for
destroying fixed network or in areas where wired LANs are impossible or only cost-
intensive to deploy such as protected historical. People are also using these networks in
cafes, restaurants, malls, universities, and public gatherings such as conferences
(Gibson, 2012; Rappaport, 1996; Tse & Viswanath, 2005).
Mobile Ad-hoc network (MANET) is considered one of WANET types, where
the nodes in MANET has the capability to move freely and randomly, which result in
changing the paths between the nodes and the topology of the network constantly
(Gibson, 2012). The effect of high mobility of the nodes brings fundamental challenges
to the routing protocols in MANET Network. The main function of routing protocols is
to find the routes from the source to the destination, but will be more complicated in an
environment where topology constantly changing as a result of the ongoing movement
of the node causing the lasting change to all the routes that have already identified by
the routing protocols. Therefore, routing protocols of MANET networks must have an
effective mechanism to find constantly changing routes and notified them quickly about
the constantly changing routes (Guevara, Jiménez, Prieto, & Seco, 2012; Yadav &
Chavan, 2013). However, because of the constant movement of the nodes, the
possibility of broken links increases and also with a possibility of the nodes destination
goes out of the transmission range (Wu & Dai, 2005; Ali. S. et al, 2015).
In this paper, we propose a modified route discovery mechanism in order to
reduce the effect of the mobility in the link transmission using efficient DSR protocol.
The DSR protocol is very suitable to small and medium networks and can offer a quick
and easy network solution comparing to any other routing protocols (Abolhasan,
Wysocki, & Dutkiewicz, 2004; Royer & Toh, 1999). The proposed mechanism that will
be clarified in detail in the methodology section depend on an update the DSR protocol
algorithm on the part of route discovery to a destination node and adding a new
technique for classifying and arranging routes stored in the node`s cache memory.
MANETS
Mobile ad hoc networks (MANETs) are infrastructure-less wireless networks, where it
characterized in a number of properties, such as self-configuring, self-forming, self-
healing network, random mobility for the nodes, transmission through multiple hops, in
addition, to the decentralized nature which improves the scalability.
The devices in MANETs have the freedom to move randomly in all directions,
which play the roles of both the client and router together during sending or receiving
the data in the network, where it must depend on in its own information to take the
decisions to choose the paths which lead to the destination, which that create the
challenges on finding and updating that information constantly (Ayoob, Sulaiman,
Mohammed, & Abdulsahib, 2014).
The fundamental objective of MANET is to permit a gathering of
communication nodes to set up and keep up a network among themselves, without the
backing of a base station or a focal controller. The absence of infrastructure in MANET
requires the nodes to perform the network setup, administration, and control among
themselves. Every node must act as a router and data forwarder in addition to playing
the role of a data terminal.
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Routing Protocols
As there are different types of networks, there are different types of routing protocols
also which have similar aspects in the main task which is the routing, but they differ in a
way to work, where each one has a special algorithm is different from the other.
Routing protocols are originally designed for wired networks which are not adequate
and sufficient to ad hoc networks, although there is a big difference in term of wired
network topology that is more of stability compared with the topology of the ad hoc
networks which changes constantly (Mauve, Widmer, & Hartenstein, 2001).
When designing a routing protocol that will work within the ad hoc network
environment, it should be noted that the ad hoc network has to work within a limited
bandwidth, in addition to limited resources in terms of node storage capacity, CPU
capabilities, and energy resource since it depends mainly on batteries. We can infer
from the above, the fundamental differences between routing protocols for wired
networks that consume large amounts of bandwidth and resources of the nodes, like
memory capacity, processor capabilities, also deal with the fixed and stable devices,
topologies and routing protocols for ad hoc networks (Menchaca-Mendez & Garcia-
Luna-Aceves, 2008; Moustafa, Kenn, Sayrafian, Scanlon, & Zhang, 2015). MANET
routing protocols were classified into three major categories, Figure 1 presents the
classification of routing protocols (Royer & Toh, 1999).
Figure 1. Classification of MANETs routing protocols
Reactive routing protocols
Also called on-demand protocols, where the general principle of these protocols
depends on reducing the overhead, control messages, and updates messages that are
exchanged between the nodes in the network as a requirement for other traditional
routing protocols. In on-demand protocols, the nodes maintain only the active paths,
which are required and used to send the data to specific destinations. When the node
needs to send data to a specific destination, and it did not have any paths to that
destination, thus in this case the source node sends broadcast message which is called
request message (RREQ) to all nodes in the network, which in turn, these nodes re-
broadcast this message until reach to the destination node, where it in turn responds by
sending a reply message (RREP) to the source node using link reversal or piggy-
backing (Abolhasan et al., 2004).
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Dynamic source routing protocol (DSR)
The DSR protocol is classified as one of the reactive routing protocol used in multi hop
wireless Ad-hoc networks. It consist two main stages one is route discovery, second is
route maintenance. The route discovery stage begins when the source node want to send
the data to a node not exists in its routing table. The route maintenance stage begins
when one of the identified routes is broken or failed.
DSR uses source routing, which allows routing of packets to be loop free and
also allows caching of routes in nodes for future use (Kant & Kumar, 2012; Mohammed
& Sulaiman, 2014; Unnikrishnan, 2004). When the source node decides to send data to
the destination node, it will first searches in the in its cache memory to find any valid
routes to destination node, if didn’t find any it will initiates route discovery process
(Gavrilovska & Prasad, 2006).
RELATED WORK
The (Ayoob et al., 2014) presented new proposal in order to mitigate the negative
effects resulting from the continuous mobility of the nodes and lasting change in the
network topology. The proposal includes providing a new algorithm consist of two
mechanisms (route status checker, route order) and make a change to the mechanism of
keeping the routes in the cache memory by setting up two tables (Master route cache
and Index Route Cache). While (Yu & Kedem, 2004) proposed a distributed adaptive
cache update algorithm for DSR, and defined a new cache structure, cache table without
limiting the capacity. The result showed significant improvement in TCP throughput
and achieved a large reduction of normalized routing overhead. Moreover, the (Manjhi
& Patel, 2012) proposes to find a mechanism to determine the best routes and their
updates as well as the acceptance or rejection of the new routes based on measuring the
signal strength of the nodes, which will reflect positively on the performance of the
entire network and measure the positive results related to end-to-end delay, packet
delivery ratio, throughput, routing overhead.
METHODOLOGY
In this paper, the processes are divided into two main parts, the first part will be
focusing on dissecting the DSR route discovery algorithm. While the second part will
cover the proposed adjustments to improve DSR protocol performance in the both
processes of discovering the routes and sending the data. In other words, it would be
reflected in practice to improve the performance of overall MANET networks, where
the importance of routing protocols in controlling the performance of all kinds of
networks as well as representing the backbone and network analyzer, which measure the
performance of any network.
Dissection DSR Route Discovery
Figure 2 illustrates the steps of the basic route discovery algorithm for DSR protocol.
There are two main disadvantages in such route discovery. In the first instance, the step
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indicated with the number 2 in figure 2 is the mechanism used by intermediate nodes to
re-propagate the RREQ message to all its neighboring nodes in all directions. Figure 3
shows the node S initiating a route discovery by flooding RREQ message to all its
neighbor nodes. When the intermediate nodes receive the RREQ message and after each
of them applied all the checks described in figure 2, which indicated by A and B. After
that, each node reaches to the stage number 2 as described in figure 2, then each one re-
broadcast the RREQ to all neighboring nodes in all directions without the organization
of the process. The process continued whereby other intermediate nodes perform the
same process until the RREQ message reaches to the destination node.
Through the analysis represented in figure 3, the following disadvantages can be
observed:
a) There is a great possibility for the majority of the intermediate nodes to receive
the RREQ message from more than one node at the same time, which increases
the probability of occurrence the collisions and that leads to discarding the
messages, which causes an additional consumption of bandwidth, in addition, to
increase the overhead, delay, and latency because of the need to re-send the
messages.
b) A large proportion of the nodes receive more than one copy of the same message
from multiple nodes, although the algorithm has addressed this issue through
tests which are performed by each node as explained in figure 4 for instant A
and B. However, so many of these non-required messages can cause
consumption of capabilities and resources of nodes by increasing the node
battery consumption and increase the load on the processor, in addition to what
have been mentioned in the previous point such as additional consumption of
bandwidth, increase the overhead, delay and latency.
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Figure 2. Basic DSR Route Discovery Algorithm
When the source node S receive the desired route through the reply message
RREP, it keeps this route in its cache memory for use to send in the next times to the
node D as shown in Figure 2 in stages 3 and 4. The default mechanism for arrangement
the routes according to the minimum of hop count (Manjhi & Patel, 2012). However,
the path with a minimum number of hop count can be a low performance in terms of
bandwidth and speed, and especially that the routes between a spaced nodes and the hop
count factor with totally ignoring the other most important factors like distance and
signal strength will cause an increased the probability of sending the messages via stale
or fewer quality routes than other available and this certainly will lead to what the
previous mention of the past points of an additional consumption of bandwidth, increase
the overhead, delay, and latency.
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Figure 3. Re propagate RREQ between Intermediate nodes
Proposed Algorithm
The first proposed solution provides is to perform adjustments in the mechanism of re-
send the RREQ broadcast messages by intermediate nodes to their neighboring nodes,
which has been explained previously with clarified the negative results from them. The
proposed adjustments are:
a) In normal case, the intermediate node sends an RREQ message to all neighboring
nodes in all directions. In the proposed algorithm, each node forms two route
search zones (RSZ): right and left. Each node keeps in a special table in its cache
memory the data of all its neighboring nodes with identified the RSZ where this
node belongs to, with continuous updating of this table when receipt of any
message from any of these nodes later. Each node uses the GPS system to
determine its location in addition to its neighboring nodes location to determine in
any RSZ resides as well as updating their locations continuously. The
intermediate node resends the broadcasting message to all nodes located in RSZ
which opposite to the RSZ where the neighboring node that sent the message
located, for example: when the node receives the message from the right RSZ,
then it will resend this messages to all nodes located in left RSZ and vice versa.
The basic idea relies on determining the RSZ on the concepts of geographic
routing where each node knows of its own location using GPS in outdoor and
infrared in indoor, like LAR, DREAM, and GRID protocols.
b) The second proposed solution provides to perform adjustments in the mechanism
of arrangement the routes in the cache memory, according to best signal strength
(SS) of routes, where the total SS of the route is the sum of SS of every node on
the route. The node will first be judged by a threshold to determine if it is
overloaded. If so, the RREQ message will be dropped and the established route
will not contain this overload node. By using this new mechanism and when there
is more than one path to the destination node, the source node S will choose the
A modified route discovery approach for dynamic source routing (DSR) protocol in mobile ad-hoc networks
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path with highest signal strength and ignore the hop count default factor as shown
in Figure 4 and 5.
Figure 4. The Modified Re-propagate RREQ between Intermediate nodes.
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Figure 5. The proposed algorithm
IMPLEMENTATION
In this section, the comparison between the results of the modified algorithm and the
standard algorithm of DSR protocol will be presented, as well as provide a discussion of
these results, in order to determine the efficacy of the modified algorithm with the
degree of the improvement which was added on the DSR performance of the MANETs.
In the simulation programs, both the standard and modified algorithms have been
A modified route discovery approach for dynamic source routing (DSR) protocol in mobile ad-hoc networks
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applying on three different scenarios in terms of network size (5 nodes, 10 nodes, and
20 nodes), while the nodes are moving in all scenarios on speed 5 m/s.
Simulation Parameters
Table 1 presents the simulation parameters which was used in this experiment.
Table 1. Simulation parameters
Parameters Value
Simulation Area 100 m x 100 m
Simulation Time 300 seconds
Node movement model Random
Number of Nodes 5, 10, 20
Routing Protocol Standard DSR,
Enhanced DSR
Traffic
Generation
Parameters
Traffic type Explicit traffic
Start time [seconds] 100
Packet inter-arrival time Exponential (1) s
Packet size [bits] Constant (1024)
Source Node 1
Destination Node 5, 10, 20
Stop time [seconds] End of simulation
Performance Metrics
Performance metrics are used to measure and analysis the performance of the networks
in order to make a comparison between different network models and systems. There
are three performance metrics within this designed simulation that are related to the
modified and proposed algorithms in this paper, which they are:
1. Route Discovery Delay: It is the delay time elapsed in route discovery process
from the first moment which the source node initiates the route discovery
process until it receives the responses from the destination node.
2. Routing Traffic: It is the total routing traffic sent and received by all nodes in the
MANET, which is equal in the route discovery process the sum of both RREQ
messages and RREP messages.
Number of RREQ Messages: It is the total number of RREQ messages
which distributed from all nodes in the network during route discovery
process until reaching the destination node.
Number of RREP Messages: It is the total number of RREP messages
which sent from the destination node to the source node as a response to
the RREQ messages during the route discovery process.
SIMULATION RESULT AND OBSERVATIONS
This section presents the results obtained from the simulation program for all scenarios,
where will provide and discuss these results for each of the selected performance
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metrics separately, and then will be thrown an analytical look at these results as a whole
for both standard and enhanced algorithms.
Route Discovery Delay
This metric determines the amount of time spent in the process of route discovery.
Table 2 shows with Figure 6 the results of the route discovery delay for all scenarios.
Table 2. Route discovery delay
DSR Algorithm 5 Nodes
10 Nodes
20 Nodes
STANDARD DSR 9 ms 22 ms 30 ms
ENHANCED DSR 8 ms 17 ms 25 ms
IMPROVEMENT % 11.11111 22.72727 16.66667
Figure 6. Route discovery delay
Number of RREQ Messages
Table 3 and Figure 7 show the simulation results of the number of RREQ messages in
all scenarios.
Table 3. Number of RREQ messages
DSR Algorithm 5 Nodes
10 Nodes
20 Nodes
STANDARD DSR 14 86 362
ENHANCED DSR 6 28 74
IMPROVEMENT % 57.14286 67.44186 79.55801
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Figure 7. Number of RREQ messages
Number of RREP Messages
Table 4 and Figure 8 show the simulation results of the number of RREP messages in
all scenarios.
Table 4. Number of RREP messages
DSR Algorithm 5 Nodes
10 Nodes
20 Nodes
STANDARD DSR 4 24 48
ENHANCED DSR 3 14 28
IMPROVEMENT % 25 41.66667 41.66667
Figure 8. Number of RREP messages
It can be observed positive results from applied the modified algorithm, which
can be summarized thus:
Significantly reduce the number of broadcast messages (RREQ), where each
node became sends on one direction instead of the four directions. Where the
number of RREQ which exchanged between the nodes decreased by 50-80%
when using the modified algorithm.
The number of RREP messages decreased by 28-41% when using the modified
algorithm.
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Due to the significant decline in routing traffic (RREQ and RREP), so a decline
in the value of the delay occurred using the modified algorithm by 11-22%.
Dramatically reduces the problem of the node which receives more than one
copy of the same message.
Generally, the modified algorithm provides better performance as the number of
nodes in the network has increased.
From the results of the previous points, there is a significant reduction in the
probability of collision which resulting from the receipt of the node more than
one message from different nodes at the same time.
CONCLUSION
The constant motion of the nodes is one of the key challenges faced by MANET
networks. The negative effects of not dealing with this challenge, such as High
consumption of bandwidth, overhead, delay and latency. The proposed modified
algorithm for DSR protocol providing for performing two adjustments, and are: firstly,
perform adjustments in the mechanism of re-send the intermediate nodes to RREQ
broadcast messages to neighboring nodes according to the direction and signal strength.
Secondly, perform adjustments in the mechanism of arrangement the routes in the cache
memory, according to best signal strength (SS) of routes.
After applied of the proposed adjustments of a DSR protocol algorithm, we got
the following results:
General decline in the network overhead includes the RREQ and RREP
messages
Alleviate the problem of collision and repeating received the same message.
Improve the speed of convergence
Increase the probability of discovering the route to the destination in less
time.
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